Ims Gateway Systems and Methods for Online Charging in Ims Networks

1. An IP Multimedia Subsystem (IMS) gateway system for providing online charging in an IMS network, the IMS gateway system comprising: a first interface operable to communicate with a call session control function (CSCF) according to a first protocol; a second interface operable to communicate with an online charging server (OCS) according to a second protocol; and a charging trigger system coupled to the first interface and the second interface, the charging trigger system: receives a first message for a call session through the first interface from the CSCF wherein the first message is in the first protocol, processes the first message to determine whether to contact the OCS for online charging for the call session, generates a second message that comprises a charging request to transmit to the OCS responsive to a determination to contact the OCS, maps fields of the first message in the first protocol to fields in the second message in the second protocol, transmits the second message to the OCS through the second interface for online charging for the call session, receives a third message from the OCS responding to the second message, generates a fourth message indicating whether charging was allowed or denied; and transmits the fourth message to the CSCF through the first interface.

2. The IMS gateway system of claim 1 wherein the charging trigger system processes rule-based trigger points to determine whether to contact the OCS.

3. The IMS gateway system of claim 1 wherein the first interface comprises an IMS service control (ISC) interface and the second interface comprises an Ro interface.

4. The IMS gateway system of claim 3 wherein the first message comprises a Session Initiation Protocol (SIP) message and the second message comprises a Diameter Credit Control Application protocol (DCCA) message.

5. The IMS gateway system of claim 1 further comprising: a budget control system coupled to the charging trigger system and the second interface, the budget control system receives a message from the charging trigger system, generates an initial message that requests a quota amount of units from the OCS, transmits the initial message to the OCS through the second interface, receives a response message from the OCS indicating a quota amount of units for the call session, and monitors the amount of units consumed during the call session.

6. The IMS gateway system of claim 5 wherein if the quota amount of units is consumed during the call session or another message is received from the charging trigger system, then the budget control system: generates an interim message that indicates the number of units consumed and requests a new quota of units from the OCS, transmits the interim message to the OCS, receives a response message from the OCS indicating another quota amount of units for the call session, and monitors the amount of units consumed during the call session.

7. The IMS gateway system of claim 6 wherein if the budget control system receives a message from the charging trigger system indicating the end of the call session, then the budget control system: generates a final message that indicates the total amount of units used for the call session and transmits the final message to the OCS.

8. A method of operating an IP Multimedia Subsystem (IMS) gateway system for providing online charging in an IMS network, wherein the IMS gateway system comprises a first interface operable to communicate with a call session control function (CSCF) according to a first protocol, a second interface operable to communicate with an online charging server (OCS) according to a second protocol, and a charging trigger system coupled to the first interface and the second interface, the method comprising: receiving a first message for a call session in the charging trigger system through the first interface from the CSCF wherein the first message is in the first protocol, processing the first message to determine whether to contact the OCS for online charging for the call session, generating a second message that comprises a charging request to transmit to the OCS responsive to a determination to contact the OCS, mapping fields of the first message in the first protocol to fields in the second message in the second protocol, transmitting the second message to the OCS through the second interface for online charging for the call session; receiving a third message from the OCS in the charging trigger system responding to the second message; generating a fourth message indicating whether charging was allowed or denied; and transmitting the fourth message to the CSCF through the first interface.

9. The method of claim 8 wherein the step of processing the first message to determine whether to contact the OCS comprises: processing rule-based trigger points to determine whether to contact the OCS.

10. The method of claim 8 wherein the first interface comprises an IMS service control (ISC) interface and the second interface comprises an Ro interface.

11. The method of claim 10 wherein the first message comprises a Session Initiation Protocol (SIP) message and the second message comprises a Diameter Credit Control Application protocol (DCCA) message.

12. The method of claim 8 wherein the IMS gateway system further comprises a budget control system coupled to the charging trigger system and the second interface, the method further comprises: receiving a message from the charging trigger system in the budget control system; generating an initial message that requests a quota amount of units from the OCS; transmitting the initial message to the OCS through the second interface; receiving a response message from the OCS indicating a quota amount of units for the call session; and monitoring the amount of units consumed during the call session.

13. The method of claim 12 wherein if the quota amount of units is consumed during the call session or another message is received from the charging trigger system, then the method further comprises: generating an interim message in the budget control system that indicates the number of units consumed and requests a new quota of units from the OCS; transmitting the interim message to the OCS; receiving a response message from the OCS indicating another quota amount of units for the call session; and monitoring the amount of units consumed during the call session.

14. The method of claim 13 wherein if the budget control system receives a message from the charging trigger system indicating the end of the call session, then the method further comprises: generating a final message that indicates the total amount of units used for the call session; and transmitting the final message to the OCS.

15. An IP Multimedia Subsystem (IMS) gateway system for providing online charging in an IMS network, the IMS gateway system comprising: an IMS service control (ISC) interface operable to communicate with a call session control function (CSCF) according to ISC protocol; an Ro interface operable to communicate with an online charging server (OCS) according to Ro protocol; and a charging trigger system coupled to the Ro interface and the ISC interface, the charging trigger system: receives a first SIP message for a call session through the ISC interface from the CSCF wherein the first SIP message is in the ISC protocol, processes the first SIP message and rule-based trigger points to determine whether to contact the OCS for online charging for the call session, generates a first Diameter Credit Control Application protocol (DCCA) message responsive to a determination to contact the OCS, maps fields of the first SIP message to fields in the first DCCA message, transmits the first DCCA message to the OCS through the Ro interface for online charging for the call session, receives a second DCCA message from the OCS responding to the first DCCA message, generates a second SIP message indicating whether charging was allowed or denied; and transmits the second SIP message to the CSCF through the ISC interface.

16. The IMS gateway system of claim 15 wherein the charging trigger system transmits the first DCCA message to a session-based control function in the OCS through the Ro interface.

17. The IMS gateway system of claim 15 further comprising: a budget control system coupled to the charging trigger system and the Ro interface, the budget control system receives a message from the charging trigger system, generates an initial message that requests a quota amount of units from the OCS, transmits the initial message to the OCS through the Ro interface, receives a response message from the OCS indicating a quota amount of units for the call session, and monitors the amount of units consumed during the call session.

18. The IMS gateway system of claim 17 wherein: if the quota amount of units is consumed during the call session or another message is received from the charging trigger system, then the budget control system generates an interim message that indicates the number of units consumed and requests a new quota of units from the OCS, transmits the interim message to the OCS, receives a response message from the OCS indicating another quota amount of units for the call session, and monitors the amount of units consumed during the call session; and if the budget control system receives a message from the charging trigger system indicating the end of the call session, then the budget control system generates a final message that indicates the total amount of units used for the call session and transmits the final message to the OCS.